Telephone system



N. A. KURMAN TELEPHONE SYSTEM Filed Jan. 9, 1919 INVENTOR.

ATTORNEY.

Patented May 18, 1926.

tdTA'lTES NATHAN A. KURMAN, (3F NEVI YORK, N. 1 TO ENTER-NATIONAL CALLO- PHONE CORPORATION, A GOBPORATIUH DELA NAFUE.

TELEPHONE SYSTEM.

Application filed. January 9, 1918.

p The object of my invention is to provide a simple construction of telephone circuits which will be effective in operation and adapted to those systems in which a central station may have articulate communication with a plurality oi other stations, such as required in intercommunication on war ships or in callophone systems generally.

My invention is more particularly directed to the system of wiring, whereby the usual induction coils may be dispensed with and incidentally, the elimination of the more or less complicated wiring required with their use in a multiple station installation.

M invention has also a further object, namely, a. more effective and e'tlicient transmission of articulate speech than has been possible in systems en'iploying induction coils between theprimary or transmitter circuit and the secondary or line circuit in which the receiver is located.

My object is also to provide a system which is flexible in its adaptation to any number of receiving or sub-stations, while maintaining simple circuit wiring.

In my improved system, I employ circuits which connect the battery, not only in sei' with the transmitter but also in series with the receiver througha condenser; the transmitter and receiver being together in multiple relation with the battery, and associated. with an inductance, included in the battery circuit either wholly or partly between the battery and transmitter and etitective, by self-induction, in producing variable potential currents, which by means of the condenser, induces alternating currents in the line circuit and receiver therein.

In my improved system, the variable re-- sistance of the transmitter (during sound transmission) permits a variable current flow from the battery; and this current being of a pulsatory or undulatory character, produces in the seltinduction or impedance coil pulsations oi increased electromotive force which, being impressed upon the variable current caused by the action of the transmitter, effectively energizes the condenser and thereby induces alternating currents which pass into the line and energize the receiver. This result may be explained by assuming that the flow of the battery current through the impedance or self-inductance coil is, under the control et' Serial No. 2%,385.

the transmitter, made to surge within the ference, which are efiective in the condenser to generate secondary currents, to be conveyed by the line circuit to the receiver.

l he increased potential generated by the self-inductance coil becomes especially etitcctive in the condenser with each increase in resistance of the transmitter and overflows, as it were, into the condenser. This overflow cf the current of increased. potential may be still further augmented by including in the circuit additional selfinductance effects on either or both sides of the condenser; and in all cases the variable current phase in the receiver circuit will be in timed relation to the varying resistance and current pulsations in the transmitter.

Considering the return current from th receiver, it appears to have two paths, one through the transmitter and one through the battery and impedance coil; it cannot flow through the battery and impedance coil, as by the nature of its alternating or pulsatory character, the impedance coil ofters an effectual bar; it therefore must flow through the transmitter, which though va riable, is non-inductive and acts to short circuit the impedance coil and battery. The

ohmic resistance ot the transmitter in coinparison to the resistance of the receiver circuit is so slio'ht as to be nee'lio'ible. C x) {9 I pecially as it is entirely non-inductive, and the variations of the resistance medium have no ellect upon the tone of the receiver sounds,

My invention consists of method and means whereby the above enumerated re sults and advantages may be secured, the same being, set out hereinafter and more particularly defined in the claims.

My invention will be better understood by reference to the drawings, in which: 1 is a diagram illustrating the essential a soeiation and combination of parts constit-uting my improved telephonic apparatus; Fig. 2 is a similar diagram illustrating modification oi? the same; and Fig. shows a combined circuit embodying the features of Figs. 1 and 2, and with selective means for introducing either into operative condition,

These diagrams to iilustr the essential. or characteristic features oi" embodiment of my invention; and are to be lalicn as examples of the system in its simplest term and not, by way oi restriction.

2 the battery, (3 is the transmitter, and it is the receiver. 2-) and r. are the two legs ol the battery circuit and these are connected by circuit 5 including the transmitter (3. The coinluctor lincludes an impedance or sell induction coil 7. whose resistance and. coil turns are properly proportioned tor the duty to be performed. 8 and 9 are continuations (it the battery circuits 3 and 4 respectively, and unite in the receiver 11. Conductor 9, which is an extension of the conductor 4-, includes the condenser 10, which prevents direct llow ot the continuous current of the battery into the receiver circuit between the condenser and receiver, but receives the overflow current of higher potential and becomes charged to a degree which causes induced discharge through the rc eiver circuit 9, receiver 11, and conductor 8. In this manner the extra current, so to speak, induced in the self-inductance coil 7 at the moment of change of resistance (increasing) in the transmitter, tinds relief in charging the condenser (having predetermined proper capacity) and discharging by induction therethrough into the receiver circuit.

In Fig. 2, the receiver circuit 9 also includes an amount of selfinductance or impedance coils 7, which will assist in the building up of potential and insure somewhat more rapid discharges of the condenser. Otherwise, the layout of the system is the same as in Fig. 1, first described.

'lcierring to the selective system illustrated in Fig. 3, the condenser 10, is shown is in series with the two coil windings 7 and T. ot the seltinductance or impedance coil which, as in Fig. 2, are wound upon a common magnetic. core. The switch l-it is conn -cie l with the iine or receiver circuit 9 and is adapted to llliilit connection either with the terminal 12 ot the self-inductance or llll lQililllCt coil 7, or with the terminal 13 d rectly connecting with the. condenser 10, as desired. the inclusion of the coil 7, being 1 able when the system is intended to talk t'rom central or master station to a single distant station (corresponding in operation to Fig. *3), whereas the direct connection ot the line i) with the condenser it) is more dosirable when the central or master station is to tall: to a plurality of distant stations (as explained in connection with. 1). In l ie'. i), I have shown the condenser arranged in series with and between the two sections of coil 7 and T of the self-induc tance coil, whereas in Fig. 2 I have shown the condenser arranged on the line terminal of the coil winding 7, but this difference is immaterial, it sufiicing that the condenser shall be in the circuit between the receiver and self-inductance coil T. whether the coil 7 employed or omitted. Where the system is to be restricted to two stations only, the circuits shown in Fig. 2, will prel'erably be employed; where more. than two stations are to be employed permanently in multiple with the central station. the circuits shown i Fig. 1 will preferably be. employed; but when the system is to combine both stems with a selective means, then the circuits shown in Fig. 3 will n'el erably be employed.

In operation, th current flowing; from battery through the transmitter is all'ected directly by the variable resistance ot the transmitter in ope 'ation. lbviously, there is a drop oi? potential across the transmitter terminals, and one terminal o l the condenser will be charged to the same potential as the terminal of the transmitter to which it is directly connected (Fig. 1) and the other terminal of the condenser will have a potential commensurate with the other terminal of the. t'ansmitter with which it is connected through the. line and receiver, allowing for such drop of potential as may result from the interposition oi the receiver resistance and that of the line circuit. llhen the transmitter varies its resistance a variation in voltage across its terminals will occur. and. as a result, a variationacross the terminals of the condenser will be effected. This varying ot the potential across the terminals oi the condenser insures an induced current flow in the line and receiver and hence the production of articulate sounds from the receiver in synchronism with the corresponding potential variations across the terminals of the transmitter. It would appear that the induced current in the line 8, 9, between the condenser 10 and cross circuit 5 from th transmitter 6, and including the receiver 11, is of: an alternating character, and in the flow of this alternating current its energy is expended in the selt-imluctance or impedance coil 7 and T. In this action, the induced alternating current augments the induced or extra-current ell'ccts produced in the inductance coils 7 and T and thereby provide a more ell'cct-ive inducing current for charging the condenser '10. in other words. the circuit system may be considered as one in which the undulalory current in the local or transmitter circuit. 23. 1-. 5. produced by the action ot the variable resistance of the transmitter upon the continuous currmrt (low from the battery 2 is availably iiiipi'ceserl upon the current in the line 8.. f), through the inductive action ot the condenser. coupled with the self-inductive etlect wh ichis im luccd in the impedance coil '7 in the battery circuit and made effective directly (Fig. 1) or through the second coil portion 7* (Fig. 2) of the impedance coil, and also made cfliective upon the condenser 10 in producing an.

increased potential to the induced alternating currents in the line or receiver circuit. The circuits are simple while the reactions produced therein are somewhat complex; but it is believed that the above explanation will sufiice to account for the highly effective and etiicient results in articulate transmission secured thereby.

Again considering the building up of the E. M. F. by the action of the transmitter upon the battery current flowing through the self-inductance coil, the following explanation may be made:

When the transmitter is reducing its resistance, the self-inductance coil 7 tends to induce a counter electromotive force, which reduces the effective E. M. F. of the battery current, and then when the transmitter increases its resistance, this action quickly reduces the counter E. M. F. and induces an extra E. M. F. and thereby the production of an extra current which charges the condenser, as before explained. It will be understood that the strength of the battery, the ampere windings of the coil 7 and the resistance of the transmitter, all influence the extent of the extra or induced current which is to be effective in producing the secondary current in the receiver circuit.

As before stated, I have shown the simplest form of my invention, but it is to be understood that where there are a plurality of receiver circuits and with their condensers simultaneously operating in parallel from the same battery circuit and transmitter (Rig. 1), the flow of current from battery through the transmitter should increase proportionately to theincrease of receiver stations, otherwise the potential energy induced by the condenser would not be strong enough for the most efficient results.

I have now described my invention in a generic sense, but it is to be understood that in actual commercial practice in a multiple unit syste1n,there will be suitable selective switches and other devices, such as signalling means, but these do not form any part of the present invention; and while I have described my invention in the forms found in practice to be best suited to the aims and objects of the invention, I do not restrict myself to the details, as these are susceptible of modification without departing from the spirit of the invention.

Having now described my invention what I claim as new and desire to secure by Letters Patent, is:

1. A telephone system comprising a transmitter; a battery; a selfin .luctance coil; and a transmitter circuit including the transmitter, battery and inductance coil in series; in combination with a receiver; and a receiver circuit including the receiver, battery and inductance coil and also containing a condenser between the receiver on the one hand and the battery, inductance coil and transmitter on the other hand.

2. The telephonic system defined in claim 1, further provided with an additional selfinductanee coil arranged in the receiver circuit in series with the condenser and through which the extra current from the self-inductance coil of the transmitter circuit passes.

8. A telephonic system comprising a com plete transmitter circuit including a battery, a transmitter, and a self-inductance coil, all arranged in series, combined with a receiver, a condenser, a receiver circuit having one limb connected with one terminal of the battery and the other limb connected with one terminal of the condenser, whereby the receiver is arranged in the receiver circuit between one terminal of the battery and the condenser, and a connection providing an electric circuit between the other terminal of the condenser and the other terminal of the battery through the inductance coil.

4. A telephonic system, comprising a source of electric energy, a transmitter, a

transmitter circuit including the transmitter in series with the source of energy, a receiver at a distance from the transmitter, a receiver circuit branched from the transmitter circuit so as to form a looped circuit including the receiver and transmitter in series with each other and in multiple relation to the source of electric energy, condenser in the receivrn' circuit, and means energized by the source of electric energy and under the control of the transmitter for producing currents of higher electromotive force for energizing the condenser and thereby producing in duced currents in the receiver circuit.

5.111 a telephone system a transmitter circuit, a transmitter and a battery therein, a self-inductance coil also in the transmitter circuit, a receiver circuit, a receiver therein, a condenser in the receiver circuit in series with the receiver, a self-inductance coil in the receiver circuit, and a. switch device for putting the last mentioned inductance coil into or out of the receiver circuit.

In testimony of which invention, I hereunto set my hand.

NATHAN A. KURMAN. 

